http://www.signonsandiego.com/news/s...alwarming.html

Study: Global warming brings extreme changes to California

SACRAMENTO – Global warming will cause a dramatic increase in extreme
summer heat and a depleted winter snow pack that will have severe
effects on California's water and power supplies, 19 U.S. scientists
reported Monday in a prestigious scientific journal.

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The report is substantially more pessimistic than previous
projections.

It also differs from previous studies in presenting citizens and
policy-makers with a choice, said the lead author, Katharine Hayhoe of
ATMOS Research and Consulting in South Bend, Ind.

California can avoid the worst effects by quickly cutting how much
carbon dioxide and other heat-trapping gases are released into the
atmosphere, the scientists said. They include experts from Stanford
University and the University of California, Berkeley, along with
consultants and members of the Union of Concerned Scientists.

The study published in the Proceedings of the National Academy of
Scientists focuses on California because of its diverse climate, large
economy, agricultural interior, and heavily polluting industries and
population centers.

The scientists used computer models they said illustrate the
consequences of doing nothing, or adopting "relatively aggressive"
policies such as a greatly increased emphasis on renewable energy
instead of fossil fuels.

"If we do not take action now to reduce emissions of greenhouse gases,
the consequences for California after about 2050 will become
significantly more harmful than if we do take action now," said
Michael Hanemann, director of the California Climate Change Center at
UC Berkeley.

Under the most optimistic computer model, periods of heat waves and
extreme heat will quadruple in Los Angeles by the end of the century,
killing two to three times as many people as currently; the Sierra
Nevada snow pack would decline by 30 percent to 70 percent; and alpine
forests would shrink 50 percent to 75 percent.

The most pessimistic model projects five to seven times as many
heat-related deaths in Los Angeles, with six to eight times as many
heat waves. Snow pack and high altitude forests would shrink up to 90
percent, and sea level would rise a foot or more. By century's end,
temperatures would jump twice as high if nothing is done than if
immediate steps are taken.

The scientists' temperature projections are higher than previous
estimates, particularly in summer. Their predictions of an extreme
decline in snow pack, alpine forests and the spread of desert areas
all exceed earlier projections.

"It's another piece of climate alarmism," said Marlo Lewis, a senior
fellow at the Competitive Enterprise Institute. "It's layers of
assumptions and it's all designed to paint a very frightening
picture."

He and Bonner Cohen, a senior fellow at National Center for Public
Policy Research, questioned the reliability of the underlying computer
models, and said the report fails to account for human ingenuity and
adaptability.

The study reduces large-scale models to the regional level, though
other scientists say uncertainty increases as the scale diminishes.

Three of their four computer models predict precipitation declines of
15 percent to 30 percent in the Central Valley and along the northern
coast, contrary to previous models that predicted substantial
increases. The various studies all note that California's weather is
largely determined by ocean conditions, making precipitation
predictions difficult.

Among other predictions:

The combination of warmer weather and less precipitation will mean a
shorter, later ski season.

Spring melt-off will come earlier, increasing the risk of flooding and
decreasing how much snow-melt could be captured in reservoirs. The
state will rely more on increasingly scarce groundwater, even as
drought frequency and severity increases.

The combination jeopardizes the water supply of 85 percent of
Californians who rely on snow-melt and Central Valley rivers,
including those in the San Francisco and Southern California regions.

Farmers will battle more pests and fight for a greater share of
dwindling irrigation water.

Finally, the state's renowned wine industry could suffer everywhere
except on the coast, the scientists say – countering previous
projections that at least the wine might improve.